The mathematical form of an $AM$ wave is given by $e = 50 (1 + 0.5 \sin(2\pi \times 5 \times 10^3 t)) \sin(31.4 \times 10^6 t) \text{ V}$. The frequencies of the $LSB$ and $USB$ in the given $AM$ wave are,respectively,....... and ....... .

Which types of communication modes are used for the propagation of radio waves from one place to another?

Long range radio transmission is possible when the radio waves are reflected from the ionosphere. For this to happen,the frequency of the radio waves must be in the range:

For efficient transmission of sound waves of wavelength $\lambda$,the minimum length of the antenna should be.....

We do not transmit low frequency signals to long distances because:
$(a)$ The size of the antenna should be comparable to signal wavelength,which is impractical for a signal of longer wavelength.
$(b)$ Effective power radiated by a long wavelength baseband signal would be high.
$(c)$ We want to avoid mixing up signals transmitted by different transmitters simultaneously.
$(d)$ Low frequency signals can be sent to long distances by superimposing them with a high frequency wave.
Therefore,the most suitable options are:

The range of frequency bands used for standard $AM$ broadcast is